However, patching together the computer’s software wasn’t Kildall’s greatest accomplishment. It was what he had done with writing new software code. Out of absolute necessity, and with no thought of the commercial possibilities, he developed a master program so that his unique little computer could adapt itself to run a useful software applications designed for much larger stand-alone machines. That’s how Kildall developed the first operating system software for personal computers.

After revising it further so it could run on the newer and faster Intel 8080 microchip, Kildall would call his operating system CP/M (Control Program for Microcomputers).

When hobbyist strated building their own 8080-based home computers, Kildall realized he had created something of value. He put a small ad in a computer trade magazine and began selling copies of CP/M for $70, first to hobbyist then to other small computer…